In view of the high-power IGBT short-circuit protection technology, the IGBT short-circuit reason and protective principle was introduced. The short circuit time of IGBT was verified to be closely related to its working voltage by short circuit test waveforms under different working voltages. The inverse relationship between IGBT short circuit time and IGBT working voltage was obtained. It was proved by data fitting curve of short-circuit test that the short-circuit energy of IGBT was the same under different working voltages.